When manufacturing clothing of various types, the most complicated operation is usually that of joining the sleeves to the body piece. Irrespective of the material used, joining the sleeves usually involves several operations of varying complexity and taking varying amounts of time, which is directly reflected in the price of the garment.
The mere fact of the sleeves being located one on each side of the body piece necessitates at least two work operations. With the object of simplifying manufacture, it is already known to start with two pieces of material--a front piece and a back piece, each provided with projecting sleeve pieces on each side. Joining these pieces along only the sides/lower arms and upper arms/shoulders reduces manufacture to four operations.
Stitched or welded seams are generally executed in the horizontal plane and can only be performed on two layers of material at a time. When the sleeve material, usually cylindrical in shape, is attached to the body piece, which may be flat, a third layer of material may easily catch in the seam. This layer of material must then gradually be turned aside or screened from the welding heat of attachment, thus further complicating attachment.
To avoid such operations, it is also known to turn the work-pieces inside out, turning them the right way again after joining. The result is in any case several work operations, both before, during and after the actual joining process.